For example, is there a difference between:
1. Tank A - has a floor of 5ppm nitrates and 1ppm nitrates are added each day to keep up with plant demand
2. Tank B - has a floor of 0ppm nitrates and 1ppm nitrates are added each day to keep up with plant demand
Should there be any growth rate difference between Tank A and Tank B above? I would argue that there is probably no difference in growth but a big difference is that Tank A has much greater possibility of algae growth due to excess nutrients sitting in the water column.
In the above example, no doubt I would expect Tank B to exhibit faster growth.
I prefer to think of an optimal level that allows for easiest uptake for plants. For instance, let's say a heavily planted high light tank uptakes 3 ppm NO3 daily. Does that mean 3 ppm in the water column is optimal? I would say no. For a tank like mine, somewhere about 25 tp 30 ppm NO3 is optimal. At lower levels there are many fast growing stems that will not exhibit peak growth/color, and may stunt or be at less than peak health.
Plants at less than peak health are a magnet for algae. I have observed a great number of tanks over the years. In my experience, I have seen more issues arise from under dosing than over dosing, and too little is worse than too much.
Now keep in mind this is always in the context of the particular tank with a particular mix of plants. There are some tanks that are more hardscaped based with mainly Rotala's or other plants that don't require much in the water column. Then there are tanks full of Limnophila's and Ludwigia's that would prefer much higher levels. They are different animals. There is no one scheme that is optimal for all types of plants.
As to excess nutrients in the water column causing algae, this has been disproven many times over. Very old thinking in terms of planted tanks. I can dose an extra 10 ppm NO3 into my tank any time and see no uptick in algae. Most problems with algae have little to do with fertilization, other than providing too little.
It usually has more to do with intensity/duration of lighting, pH drop from CO2, and most often poor maintenance/husbandry. A dirty tank full of dissolved organics is a number one cause, and you can adjust dosing all you want and you will never fix it.
As always, just my thoughts and experience from my tank and many others that I follow closely.